Colon cancer screening best tests are non-invasive. Why fecal blood test detects only advanced stage colorectal cancer? How analysis of tumor DNA can help in early cancer detection? How to detect colon cancer DNA and RNA in blood? Leading colorectal cancer oncologist and research expert discusses colon cancer diagnosis and treatment options.
We also look for indirect methods of colon cancer screening. This is clearly the examination of feces. We look for a sign of the colon cancer tumor in the stool. Dr. Anton Titov, MD. For many years, occult blood test was the only early colorectal cancer screening test. We try to see if there is some blood coming from the colon cancer tumor. Prof. Dr. Hans-Joachim Schmoll, MD. Hidden blood can be detected in the stool. It indicates potentially a cancer in large bowel or rectum. However, testing for hidden blood in feces is not an early detection of colon cancer. This is a screening for intermediate or advanced stage cancers. Sometimes a colon cancer tumor is bleeding, then it is too late. For detecting colon cancer at early stage blood testing of feces is not a good method. Dr. Anton Titov, MD. But we need early colon cancer detection, when there is a high chance for cure. Occult fecal blood testing is done in Germany and the UK and in many countries. Prof. Dr. Hans-Joachim Schmoll, MD. Fecal occult blood testing is a good single test. But it is not good enough to prevent colon cancer diagnosis at only a late stage. this screening method is not a good test to prevent deaths from colorectal cancer. The best method to test for early colon cancer is to have a more sensitive method of colon cancer detection. It is better to look directly for tumor cells and tumor molecules. Tumor releases cells and molecules into the feces. Prof. Dr. Hans-Joachim Schmoll, MD. There is a recent test that is moving in that direction. It is the immunological fecal occult blood test combined with the KRAS mutation in tumor DNA molecule. It is probably currently the most effective screening test to analyze feces for early stages of colorectal cancer instead of advanced stages. This fecal occult blood test and KRAS mutation detection is a combination of immunology test and molecular test. It is a more expensive test. It took a long time for KRAS and fecal occult blood test to be accepted by the health authorities in United States and in Germany and other countries. Dr. Anton Titov, MD. But now KRAS + fecal occult blood test may be the preferred standard fecal test for colorectal cancer screening. This test is very good and very important indirect test for colon cancer screening. Prof. Dr. Hans-Joachim Schmoll, MD. But again, this is not a test for early colon cancer detection. The best indirect test would be the one this detects the tumor DNA at very early colon cancer stage. Such test should be highly reproducible. Such colon cancer screening test should be easy to do. patients who use this test should have positive opinion about it. it is clearly a molecular-based test. Now we have reached the time when we can test circulating tumor DNA in blood or urine or stool. Modern molecular biology methods can easily measure this circulating tumor DNA. It is quite expensive to test for circulating tumor DNA. Because the machines that do such testing are very sophisticated. Prof. Dr. Hans-Joachim Schmoll, MD. However, high throughput testing is being improved. It means that the price for such circulating tumor DNA screening for colon cancer will decrease significantly. Testing for circulating tumor DNA would be the best method of screening. It is not yet used very often. Dr. Anton Titov, MD. But I am sure the situation will change in 1 or 2 years. Different health authorities will adopt the use of such screening test depending on its accuracy, price, and so on. The molecular colon cancer screening test has to be reliable. Sometimes tumor DNA is tested in feces, in urine or in blood. The adoption of molecular screening tests for early colon cancer will depend upon the convenience of such tests for patients. But molecular-based test is probably the best strategy to ask for. Prof. Dr. Hans-Joachim Schmoll, MD. Perhaps a regular blood test every six months or once a year can be done. Fecal testing is a good alternative to blood testing. But good early colon cancer screening test should be done in standard sealed simple system. Dr. Anton Titov, MD. Such test should be a high accuracy tool to detect tumor DNA by various means. positive screening test result should then be followed by an colonoscopy. Currently, the colon cancer screening program in Germany starts at age of 50. Prof. Dr. Hans-Joachim Schmoll, MD. But start of colon cancer screening depends on presence of family history of colon cancer. Sometimes there is a family history of colon cancer, then screening should be started at an earlier age. This is a colon cancer screening program this is done every 10 years. People get colonoscopy and rectoscopy for free. This colon cancer screening program is very effective. Doing colon cancer screening every 10 years is acceptable. But colon cancer tumors can appear between screenings. non-invasive tumor DNA test could be good. Such DNA-based screening test can be done without any problem every year. But there is a lot of follow-up tests required in such screening program. Prof. Dr. Hans-Joachim Schmoll, MD. This happens in Germany, for example, and in United States. The US has the same colon cancer screening program as Germany does. Dr. Anton Titov, MD. The German colon cancer screening program was adopted from the United States. It is a lot of expensive work. There is also a risk of side effects from colonoscopy. There is also a risk of misdiagnosis and misinterpretation of results. This increases the costs of screening program for the healthcare system. This screening program is now the optimal choice. The fecal occult blood test is very good. The regular colonoscopy or sigmoidoscopy is excellent if done every ten years. Dr. Anton Titov, MD. But the best tests to screen for early colon cancer would be more advanced laboratory tests that detect tumor DNA.